Max amount

I need a script to set the max discount amount of coupon. I am using this as a buy 3 get 1 free coupon. I want it to have a max value discount.

Coupon is set up for 25% off cart total if 4 items are added. Works great. But I want to limit the max total discount if customer adds different products.

Example
Customer “A” Adds 4 items to the cart all same price
item 1 $6
item 2 $6
item 3 $6
item 4 $6

Coupon gives discount of $6 PERFECT

Example
Customer “B” Adds 4 items to cart different prices
item 1 $6
item 2 $7
item 3 $18
item 4 $16

Coupon gives discount of $11.75 NOT GOOD for a BUY 1 Get 1 FREE
If I could set coupon to a max value of say $7 it would be fine.

https://ww.wp.xz.cn/plugins/woocommerce-auto-added-coupons/